Add existing content

Group membership: Add existing user to the group.
Group node (Analysis Report): Add existing content item of type Analysis Report to the group.
Group node (Article): Add existing content item of type Article to the group.
Group node (Downloads): Add existing content item of type Downloads to the group.
Group node (Forms): Add existing content item of type Forms to the group.
Group node (Funding): Add existing content item of type Funding to the group.
Group node (Gallery): Add existing content item of type Gallery to the group.
Group node (Organizations): Add existing content item of type Organizations to the group.
Group node (Basic page): Add existing content item of type Basic page to the group.
Group node (Sample Point): Add existing content item of type Sample Point to the group.
Group node (System ID): Add existing content item of type System ID to the group.
Group node (Watershed): Add existing content item of type Watershed to the group.
Group node (Maintenance Log Entry): Add existing content item of type Maintenance Log Entry to the group.
Group node (Treatment Technologies): Add existing content item of type Treatment Technologies to the group.